Anisodine (Ani), a new selective M receptor blocking agent, was isolated from Scopolia tangutica in China. The structure of Ani is similar to scopolamine. Ani (2.5, 5 mg.kg-1 i.v., or 0.6 mg.kg-1 icv) increased the rate of phrenic nerve discharges (PND), while the time of inspiration and expiration,